IGFBP4 and COVID-19: Moreover, we identified eleven factors: TNF-related apoptosis-inducing ligand (TRAIL)-R1, IGFBP-1, IGFBP-4, VCAM-1, sFRP-3, FABP2, transferrin, GDF15, IL-1F7, IL-5Rα, and CD200 differentially expressed among asymptomatic, mild, moderate, severe, and convalescent COVID-19 patients compared with healthy controls using an antibody array analysis of 440 factors.